This application is entitled to the benefit of and incorporates by reference essential subject matter disclosed in German Patent Application No. 101 25 789.9 filed on May 26, 2001.
The invention relates to a valve arrangement for shutting off a working line in a refrigeration system with an expansion valve, which is arranged in the working line, and a control line system connecting the expansion valve with a low-pressure side and a high-pressure side of the working line, the expansion valve being controllable by the control line system, and the control line system being able to provide a closing pressure in the expansion valve by means of a control device.
An arrangement of this kind is known from xe2x80x9cSporlan Bulletin 30-10xe2x80x9d of January 1993, pages 17 and 18 wherein a valve arrangement is shown, in which the working line of a refrigeration circuit can be closed by means of a solenoid valve. The actual closing and opening of the working line takes place via the expansion valve, which is controlled by the solenoid valve. The solenoid valve is a 3-way valve, which has a connection line for the expansion valve, as well as a high-pressure connection and a pressure-equalising connection for the working line. During normal operation of the expansion valve, the connection line is connected with the pressure-equalising line via the solenoid valve. In order to close the expansion valve, the connection between the connection line and the pressure-equalising connection is closed via the solenoid valve, and at the same time a connection is created between the connection line and the high-pressure connection. The high pressure, which now is controlling in the expansion valve, ensures that the expansion valve closes the working line.
U.S. Pat. No. 6,053,417 shows a valve arrangement with a solenoid valve working directly in the working line within the expansion valve. When closing the solenoid valve, a high pressure propagates inside the expansion valve and ensures that a valve element, which is also arranged in the working line, comes to rest against a valve seat. This arrangement of both valves in the working line should reduce the disturbing noises when opening and closing the expansion valve. When, however, this is to be used with large refrigeration systems, the solenoid valve must also be large, which causes an increase in the cost of such refrigeration systems.
Thus, the prior art arrangements have either employ small, relatively expensive control devices, which are arranged outside the working line, or relatively large control devices, which work within the working line. In both cases, the manufacturing cost is high for the valve arrangement.
Based on the foregoing it is the general object of the present invention to improve upon or overcome the problem and drawbacks associated with the prior art.
The invention is based on the task of simplifying the closing of a working line in a refrigeration system.
According to the invention, this task is accomplished by means of a valve arrangement, in which the control device has a closure element in a connection path, via which the control line system connects a high-pressure side with a low-pressure side and the closing pressure can build up in the expansion valve.
In this way, it is possible to build up the closing pressure for the expansion valve by shutting off the connection path in the control line system. The size of the closing element merely has to be adapted to the connection path, which can be relatively small compared with the working line. xe2x80x9cWorking linexe2x80x9d here means the line, in which the actual flow of a refrigerant in the refrigeration system occurs. On the other hand, the control line system comprises lines like those of the connection path, which merely ensure a gradual pressure equalising or propagation of control pressures.
It is favourable that the closing element is arranged in a pressure-equalising connection, which connects a working pressure chamber of the expansion valve with the low-pressure side. With such an arrangement, a high pressure, which acts upon the working pressure chamber of the expansion valve from the high pressure side via the control line system, is removed again via the pressure-equalising connection. In the closed state of the closing element, however, the high pressure builds up before the closing element and acts back upon the working pressure chamber. Thus, in a simple way, the high pressure available in the refrigeration system can be utilised for closing the expansion valve. In this way, a fast and reliable closing of the expansion valve can be ensured.
It is advantageous that the smallest cross-section of the pressure-equalising connection is larger than that of a high-pressure control line, which connects the working pressure chamber with the high-pressure side. Thus, it is achieved that the high pressure, which acts upon the connection path from the high-pressure side, is removed again via the pressure-equalising connection in the open state of the closing element, and cannot build up in the working pressure chamber at all. In this way, an unwanted closing of the expansion valve can be prevented. In this case, the expansion valve works as an expansion valve without a high-pressure control line. The pressure-equalising connection, the high-pressure control line and the working pressure chamber form the connection path.
Further, it is advantageous that the relationship between the smallest cross-section of the high-pressure control line and the smallest cross-section of the pressure-equalising line is approximately 1:20. In the open state of the closing element, this means that the pressure in the high-pressure control line is removed reliably via the pressure-equalising line. In this way, a high operation reliability of the arrangement can be achieved.
Further, it is favourable that the area of the pressure-equalising connection acted upon by the closing element is arranged outside a valve housing of the expansion valve. With this method, it is possible also to use commercially available expansion valves. Such valves can be modified or expanded in a simple way, which reduces the costs.
In a further embodiment, the area of the pressure-equalising connection, upon which the closing element acts, is arranged inside the valve housing of the expansion valve. In this way, a relatively compact design of the valve arrangement can be achieved.
Further, it is advantageous that the closing element is made on the valve housing of the expansion valve. In this way, an optimum matching between the control device and its closing element can be achieved during manufacture of the expansion valve. Thus, the mode of operation of the valve arrangement can be optimised. Further, this ensures a compact design of the expansion valve and the closing element.
It is also favourable that the high-pressure control line is arranged outside the valve housing of the expansion valve. Such a high-pressure control line can also be fitted on a commercially available expansion valve in a simple manner. Thus, the manufacturing cost of the valve arrangement can be further reduced.
In an alternative embodiment, the high-pressure control line is arranged inside the valve housing of the expansion valve.
Further, it is favourable that the high-pressure control line is formed by a predetermined leakage path in the expansion valve. Such predetermined leakage paths are very easily made in a traditional expansion valve, for example, by removing seals. Thus, separate bores for creating the high-pressure control line can be avoided. The leakage paths can, for example, be in the shape of bores, in which movable parts of the expansion valve are guided and which connect the working line with the working pressure chamber.
It is also advantageous that the connection path through the closing element can be hermetically closed. The term xe2x80x9chermeticalxe2x80x9d means that with the conditions occurring during normal operation, an at least substantially tight closing of the connection path is achieved. In this way, it is possible to build up a particularly high closing pressure for the expansion valve. Further, the closing pressure is available relatively fast.
Further, it is favourable that the closing element is in the form of a solenoid valve. Thus, it is possible to select a proven control device, which ensures a reliable operation of the valve arrangement.